The principal purpose of this project is to develop a practical technique for quantitating the degree to which individual branched-chain ketoacids become incorporated (after transamination) into proteins, relative to the incorporation of the corresponding amino acids administered as such (this ratio is termed "R"), and to see how R varies with protein intake, route of administration, different BCKA's, and renal and hepatic disease. A 3H-labelled BCAA and the corresponding 14C-labelled BCKA will be given simultaneously i.v. or by nasogastric tube, using a priming injection and constant infusion. The ratio 14C/3H in an isolated protein, divided by the same ratio in the injectate, gives R. In addition, the specific activity of circulating leucine (or valine) at plateau makes possible an estimate of albumun synthesis rate (subject to certain assumptions). Albumin degradation rate can be estimated from the subsequent decline in labelling of albumin. R will be measured in salivary mucin, plasma albumin, and erythrocyte globin, to see how these 3 R's are interrelated. Variables to be studied will include protein intake (in normal subjects), i.v. vs. nasogastric route (in normal subjects and patients), ketoacid therapy (in patients), and valine vs. leucine.